ARCHIVED REPORTS_XR0004441 - Laserfiche WebLink

Home Browse Search

' Second Quarter 2405 Groundwater Monitoring Report Boyett Petroleum,419 S.Main,Manteca,CA Page 2 ' was observed in the groundwater inspection samples from the monitoring wells. Field observations are . included on the Groundwater Monitoring Field Forms,attached. ' GROUNDWATER ELEVATIONS AND GRADIENT Groundwater elevation data collected during the second quarter 2005 monitoring event indicate an ' average groundwater elevation at the Site of 17.46 feet, a decrease of 0.34 feet since the previous monitoring event (March 2005). Groundwater elevation contours based on the depth to water measurements collected on March 22, 2005, indicate there is a small groundwater mound near the northeast corner of the Site. The groundwater gradient at the Site is to the south, west, and northwest, away from the groundwater mound. Groundwater elevation data are presented in Table 1, below, and historical groundwater elevation data are attached. ' Table 1: Groundwater Elevation Data June 30 2005 Monitoring Well TOC Elevation Screened Depth to Groundwater Interval b s) Groundwater Elevation MW-2 35.97 15-25 18.35 17.62 MW-3 36.18 15-25 18.43 17.75 MW-4R 35.21 10-25 17.49 17.72 ' MW-6 36.07 10-25 18.74 17.33 MW-7 36.42 10-25 18.76 17.66 MW-8 36.43 10-25 18.81 17.62 MW-9 35.95 40-50 18.87 17.08 ' MW-10 36.09 10-25 18.38 17.71 MW-1 1 3 6.15 29-39 19.06 17.09 EW-1 36.23 29-39 19.17 17.06 ' . 'TOC Elevation: Elevations are referenced to NAVD88 datum,NGS Benchmark HS 4486. (Groundwater Elevation:Elevations are treasured from the top of the well casings and are referenced to the benchmark indicated above. All measurements are in feet. Lr&%P ATOIZV A�'�rAL`�'TICAL RESULTS The groundwater samples collected from the monitoring wells were analyzed for benzene, toluene, ethyl benzene, total xylenes (BTEX), and selected gasoline oxygenates/additives by EPA Method 826013, and for total petroleum hydrocarbons quantified as gasoline (TPH-G) by EPA Method 8015M by Argon Laboratories of Ceres, California. The selected oxygenates/additives included MTBE, ethanol (EtOH), ' tertiary-butanol (TBA), di-isopropyl ether(DIPE), ethyl tertiary-butyl ether(ETBE), tertiary-amyl methyl ether(TAME), 1,2-dichloroethane(1,2-DCA), and 1,2-dibromoethane(EDB). The laboratory analytical results for the second quarter 2005 quarterly groundwater monitoring event are ' presented in Table 2, on the next page. A map presenting MTBE concentrations in groundwater is included as Figure 4, attached. 4Mt� CONDOR